The present invention relates to space and communications satellites, and more particularly, to a data distribution interface for satellites.
Spacecraft electronics typically include a spacecraft processor coupled to multiple payload units. Each payload unit contains electronics which receive commands from and provide telemetry to the spacecraft command, control, and telemetry subsystem. Known satellites use multiple hardwire techniques for the distribution of commands and acquisition of telemetry signals between various units and subsystems. This signal distribution method has many disadvantages including a large wire harness that is relatively expensive and heavy. The signal distribution method is also susceptible to noise and electrostatic discharge that are commonly experienced in space. Because of the complexity of the wiring associated with such a signal distribution method, testing and troubleshooting are time consuming and costly.
One type of embedded control module is called an essential services node (ESN) and is implemented in a multi-chip module. The ESN requires significant power to operate and a significant number of external components outside the multi-chip module such as transformers and couplers. The ESN also requires a shielded, twisted pair cable. The ESN also requires a tightly regulated secondary voltage input. These requirements significantly increase the cost of the ESN to a point where it may be cost prohibitive for many commercial applications.
It is, therefore, one object of the invention to reduce the wiring harness complexity and integration cycle time for a satellite. It is a further object of the invention to reduce spacecraft cost and weight.
The present invention allows the payload wiring harness to be a premanufactured item not dependent on the payload layout and the satellite unit configuration.
In one aspect of the invention, a satellite has a telemetry and command controller coupled to multiple payload units. Each payload unit includes an embedded, mixed-signal application-specific integrated circuit (ASIC) which acts as a telemetry acquisition and command distribution device. A single bi-directional interface couples the telemetry and command controller to the ASIC.
In another aspect of the invention, a single wire is used for the bi-directional interface. The bi-directional interface may also be a wireless optical interface.
In a further aspect of the invention, a method of operating a spacecraft comprises the steps of: sending a request signal from a telemetry and command controller into a single transmit and receive connection interface; receiving the request from the single transmit and receive interface into a payload unit; processing the request in the payload unit; and replying to the request through the single transmit and receive interface.
One advantage of the invention is that the complexity of the spacecraft is significantly reduced and, therefore, the reliability of the spacecraft is also increased.
Other objects and features of the present invention will become apparent when viewed in light of the detailed description of the preferred embodiment when taken in conjunction with the attached drawings and appended claims.